Push-button tuning for signalseeking receivers



M. J. PIFER 2,501,003

PUSH-BUTTON TUNING FOR SIGNAL-SEEKING RECEIVERS March 21, 1950 2Sheets-Sheet 1 Filed April 13, 1945 5 @b N who @h .wmh

INVENTOR 777a7z'027 JPifr ATTORNEY I BYCZ Q1 March 21, I950 M. J. PIFERI 2,501,003

PUSH-BUTTON TUNING FOR SIGNAL-SEEKING RECEIVERS Filed April 13, 1945 2Sheets-Sheet 2 .90 INVENTOR Q2 1 3; 06 I I maria J P476167 1%; C 60d 5 aATTORNEY Patented Mar. 21, 1 95 ,UNITED PUSH-BUTTON TUNING FOR SIGNAL-SEEKHNG RECEHVERS Marion J. Pifer, Williamsville, N. Y., assignor toColonial Radio Corporation, Bufialo, N. Y.

Application April 13, 1945, Serial No. 588,197

13 Claims. 1

circuit or circuits desired to be tuned have reached resonance. Circuitsof this nature are shown and described in the co-pending application ofWilliam S. Winfield, Serial No. 463,775, filed October 29, 1942, and inBowman Patent No. 2,098,331, in which the fundamental principles of suchapparatus are discussed.

The invention herein is described as applied to signal-seekingreceivers, and more specifically, to a signal-seeking broadcast receiversuch as described in the Wiley Patent No. 2,491,942 dated December 20,1949.

In signal-seeking receivers, also sometimes called stop-on-carrierreceivers or signaltuned receivers, the tuning instrumentality is drivenby a motor or other power-operated mechanism, and scans the entirefrequency spectrum within the range of the receiver. When an incomingsignal is tuned in, the voltage produced by the signal operates acontrol tube, which in A receiver so constructed and operated may attimes actually receive too many stations to be convenient to operate. Ina good location, and at a time when received signals are strong,stations may be picked up every 10 kc. over the broadcast band.Ordinarily the listener desires only to be able to tune local stations.

Usually the operator prefers some sort of push button selector so that,in order to receive a particular local station, all he has to do is pushthe button, whereupon suitable mechanism moves the tuning condenser orother tuner to a previously calibrated position at which the particularstation is received. For good results, the accuracy of tuning must bebetter than a few hundred cycles, or the signal will be distorted.

In such apparatus the mechanism must, therefore, be very accurately setup or calibrated to insure that in subsequent operations the desiredstation will be properly tuned. Wear and backlash in the apparatusinterfere with its proper pre-setting and proper operation, and thermaldrift may also change the correct tuning setting for various stations,so that periodic resettin is usually necessary.

In accordance with this invention, a signalseeking receiver is providedwith push button tuning of an entirely new type. The receiver operatesas a signal-seeking receiver for the stations which are set up for pushbutton tunin that is to say, the action of the received signal stops thescanning when the particular station desired is properly tuned in, butinstead of stopping on the first signal, it receives as heretofore, thereceiver will tune only to the station indicated by the push button, ifthat station is on the air.

For example, if the receiver is pre-set for push button selection ofcertain local stations, pushing the button for a particular localstation will cause the receiver to tune only to that station,

passing over any others which may be picked upwhile tuning, and thetuning apparatus will come to rest only when stopped by the signalreceived from the desired local station. No signal from any otherstation will stop it. If that station is not on the air, the receiverwill continue to scan, indicating that the desired station is nottransmitting.

This is done by a series of adjustable contacts, one for each station tobe pre-set, each of which operates to prevent stopping of the receiverscanning except on the frequency channel of the desired station, as willbe described later, in detail.

As compared with the accuracy required of heretofore known push buttontuners, the accuracy required of my push button tuner mechanism is of adifferent and much lower order. The push button pre-setting in myinvention may be inaccurate by as much as nearly 10 kc., withoutinterfering with the tuning operation. The

desired station will still be tuned more accurately than it can be tunedmanually by a skilled operator.

This push button station selection operation may be obtained withoutinterference with the ordinary signal-seeking tuning operation, whichmay be provided in addition. The receiver may have a series of pushbuttons or plungers, called From the foregoing it will be understoodthat it is an object of this invention to provide a signal-seekingreceiver with push button tuning,

whereby the listener who desires ordinarily to listen only to one of asmall number of local stations' may calibrate or'pre-set the apparatusfor 6 such stations, each button being allocated to and set for aparticular station.

It is a further object of this invention to pro- Vide apparatus of theclass described in which the push button operation does not interferewith operation of the receiver in the conventional signal-seekingmanner.

It is still a further object of this invention to provide push buttoncontrol mechanism for signal-seeking receivers which n relatively simpleto manufacture and install, and low in cost.

It is a further object of this invention to provide such apparatus whichmay be easily and quickly pre-set or calibrated by the non-technicallistener to any desired station without requiring the use of tools ormeters.

Still other objects and advantages of my invention will be apparent fromthe specification.

The features of novelty which I believe to be characteristic of myinvention are set forth with particularity in the appended claims. Myinvention itself, however, both as to its fundamental principles and asto its particular embodiments, Will best be understood by reference tothe speci-. fication and accompanying drawing, in which Fig. 1 is acircuit diagram of so much of a radio receiver as is necessary to anunderstanding of my invention,

Figs. 2, 3, and 4 are sectional views on lines 2-2 of Fig. 5, showingthe push button mechanism in various stages of its operation,

Fig. 5 is a top plan View of the push button and contact assembly,

Fig. 6 is a detail perspective view of one of the shaft clips used inaccordance with my invention,

Fig. 7 is an enlarged detail sectional view on lines 'l-T of Fig. 5,similar to Figs. 2, 3, and 4, and showing still another position of thepush button mechanism, and

Fig. 8 is a detail top plan view of a portion of the apparatus shown inFig. 5.

Referring now more particularly to l, I have shown diagrammatically areceiver of the superheterodyne type, indicated as I, supplied byantenna 2 feeding control electrode 4g of first tube 4 through tunedcircuit 8 to ground. The output of the final intermediate frequencystage may be supplied to detector and audio amplifier 6 and the outputthereof may operate loud speaker 7 or other suitable indicator.

Since such receivers are well known to those skilled in the art, theyare not shown and described in detail. It may be noted, however, thatfirst tube 4 may have its cathode 4c connected to ground throughvariable resistor 5, which resistor may be by-passed by condenser 3Adjustment of the value of resistance 5 operates to control thesensitivity of the receiver, and the sensitivity is varied in accordancewith my invention, in a manner which will be described hereafter.

Selection of the desired signal may be obtained by adjusting the firsttuned circuit 8 and another tuned circuit, including inductance l0 andvariable condenser H, which may be connected to tube 4. In thearrangement shown, tube 4 may be the oscillator and first detector, andcircuit 8 may be tuned to the incoming signal frequency while circuitill-ll is tuned to the oscillator frequency, the circuits being ganged;but it will be understood that separate oscillator and detector tubesmay be used, and additional tuned circuits may be provided, ganged withtuned circuits 8 and ill-l l and connected to the various tubes.

Also, while I have indicated variation of tuning as being obtained byrotation of variable condenser II, it will be understood that othertypes of tuning may be employed, such, for instance, as permeabilitytuning, in which a core of magnetic material is moved into and out ofinductance Hi, and other types of tuning, such as the movement of acopper slug into and out of inductance it. In the actual apparatus Iprefer to employ straight line frequency tuning, although for simplicityof illustration, condenser ii is shown as straight line capacity.

The variable tuning element or ganged elements are preferably driven bya power source,

such, for instance, as motor 52 energized from source of power is anddriving the tuning instrumentality through interposed clutch l8 andbrake mechanism 1 so arranged that when the motor circuit is opened, themotor is declutched from the tuning element and the brake applied to thetuning element to insure against its coasting out of the desired tuningposition.

In acco d n it t si na -s k ng princ pie, the motor and the clutch andbralge mechanism are controlled by incoming signals through control tubeI4 and relay l5, biaSfid to back contact position. When relay is is notenergized, armature l5a is in back contact position a ainst back contact151; and applies ground to one ter-. minal. of motor l2, the other sideof which is connected through current source 13 to ground. Consequently,whenever i5 is in back contact position, the motor circuit will beenergized and the motor will operate the brake will be released, and theclutch engaged so that the receiver will continuously scan its tuningspectrum.

When an incoming signal of predetermined strength is tuned in, tube It,which may be a thyratron, will pass plate current and relay 95 will beenergized to front contact 151, opening the motor circuit at I51). Inconventional signalseeking receivers, this stops the variation of tuningof the receiver. In accordance with my invention herein, this may or maynot stop operation of the motor and variation of the tuning, dependin onwhether tube M has been deprived of control'at that particular tuningpoint.

If the tube 14 is deprived of control, as by having its space currentcircuit interrupted (as by switch 98, in a manner which will be morefully described hereafter), the tube cannot be ionized by the incomingsignal, relay 1 5 will not be Operated, and the motor will continue torun, and the tuner will continue to scan the spectrum. Just how thisoccurs will now be described.

Tube is derives its control voltage from receiver I through resistance39, which may be connected across the final I. F. amplifier stage, thevoltage across resistor 38 may be impressed between cathode 31c andcontrol electrode Big of tube 3!, which may be a pentodc having inaddition screen lect o e i sc su p e sor 58 and su de Sia- Cathode 3k:may be connected to ground and to one terminal of resistance 39. Controlelece trode 319 may be connected to the other terminal of resistance 38,and suppressor 3 is? may be connected to cathode 5, and screen Elsethrough resistance 35 to +18 and thence to cathode and ground. Theoutput of tube 3i may be passed through a transformer comprising primarywinding 34 and secondary 36 Primary it may be connected at one end toanode 35a and at the other end through resistance 35 to +3.

Condenser 32 may be provided, shunting primary til, and condenser 33,shunting resistance 35 and the +13 source. Secondary 36 may be 5 huntedby on ens 3, a d ,3 n ri h common point of which may be grounded, andone terminal of secondary 36 may be connected to one electrode ofpiezoelectric crystal 39, the other terminal of which may be connectedthrough condenser 40 to the opposite terminal of secondary 36.

The common point of crystal 39 and condenser 40 may be connected tocontrol electrode [4g of control tube M, which may be a triode havingcathode I40, control electrode Mg, and anode Ma, and is preferably,although not necessarily, of the thyratron type. Control electrode [4gmay be connected through resistance 4| to a variable point on resistance42, which may be in shunt with a suitable biasing battery 43.

It will be understood that the input to tube 3| is preceded by theselector circuits provided in the R. F. amplifier, converter, and I. F.amplifier, and that these circuits have a band pass characteristic ofsufiicient width to accommodate the necessary side bands accompanyingvoice or music modulated signals of usual radio quality. As a practicalmatter, these circuits will have a band width usually not less than 5kc.

The transformer 34, 36 and crystal 39 are so arranged as to beconsiderably sharper than this. Preferably they will have a band widthwhich is only a small fraction of the band width of the precedingcircuits. As an example, but not in limitation, I have found that verysatisfactory results are obtained when the band is only 0.5 kc., andthis degree of sharpness is easily obtained.

In the case of a superheterodyne, the crystal circuit is tuned exactlyto the intermediate frequency and does not vary when the receiver istuned. In the case of a T. R. F. set, the circuit (must vary in itstuning with the other circuits in the receiver, a variably tuned circuitof great sharpness being substituted for the crystal.

It is desired that the receiver shall stop in response to the signalcarrier wave, but not in response to noise alone; that is to say, ifnoise is encountered and a signal is not tuned in, the scanning must notstop. How this is accomplished will now be described. This particularfeature is per se not a part of this invention, but is described andclaimed in the Wiley application above mentioned, and only so much ofthe description is included here as is necessary to an understanding ofmy invention herein.

Tube 3| is operated as a limiter and is preferably adjusted so that itlimits at substantially the minimum strength of desired signals; i. e.,it limits below the strength of the weakest signal for which theequipment is designed.

After passing through limiter 3|, the carrier will have reached thesaturation level of the limiter; and since this amplitude is the upperlimit of limiter 3i, noise cannot increase the amplitude.

After passing through crystal 39, a significant change has occurred.There may be a loss of approximately 50% in amplitude of the wave passedthrough the crystal stage, and at the same time the band width has beenreduced to 0.5 kc., the band width passed by the crystal.

It now becomes possible to adjust resistance 42 so that the bias voltageapplied to tube l4 lies at some value at which the noise voltage aloneis insufficient to overcome the bias on tube 14, whereas the signalvoltage, being greater than this value, will overcome the bias, fire thetube, and stop the scanning, if the tube is in control.

At this point reference may be made to capacity I6 and inductance l1. Itwill be noted that when relay [5 is closed on front contact, condenserl6 and inductance l! are connected in parallel with inductance l0 andcondenser II. This adds both capacity and inductance to the circuit and,therefore, lowers its resonant frequency.

This feature is of particular value when the design of the receiver issuch that the tuning element moves an appreciable amount between thetime when the signal is first tuned in and the time when the tunerelement comes to rest. If this time is more than a very small amount, itmay produce a frequency change in the direction of detuning, and it may,therefore, be desirable to compensate for it.

Since, for a particular piece of equipment, the detuning effect issubstantially constant and may be easily measured, the proper value ofinductance and/or capacity to be added for compensation may bedetermined without difiiculty. This particular feature is per se no partOf the present invention, but is described and claimed in theabove-mentioned Wiley patent.

At this point it should be remembered that the signal-seeking plungercauses operation of the apparatus as a conventional signal-seekingreceiver; that is, to move to the next station in the spectrum,regardless of what it may be, while each station-selector plunger causesthe receiver to tune, by signal-seeking action, to the station for whichthe apparatus is calibrated or pre-set, for that plunger.

The construction and operation of the push button controls will now bedescribed. A munber of plungers may be provided for selection ofparticular stations. Ordinarily six or eight Will be suflicient, butmore or less may be provided, as desired. These plungers are preferablyspring biased against inward movement, as is usual in push buttontuners.

For simplicit of illustration, Figs. 2 to 5 and 7 show only twostation-selecting plungers 53 and 54 and one signal-seeking plunger 50,and in Fig. 1, in order to simplify the explanation of the circuits andtheir operations, the plungers have been omitted and only the contactsoperated by the plungers are shown. In Fig. 1 the contacts operated bythe signal-seeking plunger and three sets of contacts for threestation-selecting plungers are illustrated, it being understood that foreach additional station-selecting plunger desired, an additional set ofcontacts will be added. Each plunger has three positions (1) full out,(2) latched in, and (3) fully in, or overtravel.

Tuning instrumentalit l l is preferably, although not necessarily, onecapable of continuous operation in the same direction, and hassynchronized with it a cam switch consisting of contacts 20 operated bycam disk 2 i. This is preferably so related to the tuninginstrumentality that switch 20 is closed only during one-half of acomplete cycle of the tuning instrumentality. For instance, as hereinshown, the circuits may be arranged so that the receiver tuning isterminated only as the tuning frequency rises, switch 20 being closedduring the tuning half cycle when condenser I l is decreasing incapacity, and being open in the half cycle when it is increasing.

When switch 20 is open, the space current circuit of tube 1-4 isinterrupted at switch 2t, and if for any reason the tube is passingcurrent, it will immediately stop, and relay armature l5a will move toback contact position. Tube 14 cannot be ionized as long as switch 20 isopen, and,

assists 7 thereior-e; no incoming signal can cause the tuner to stoponthe return half of the cycle.

Mounted on the frameworkof the plunger hous' ing (omitted from Fig. lfor simplicity of drawing, but see Fig. I may provide plunger-operatedcontact finger 236a. This is the contact operated-by the signal-seekingplunger 50, and when it is operated, the receiver functions as aconventional signal-seeking receiver as previously described.

Alsomounted on this framework I may provide a number ofstation-selecting movable contacts, herein shown as 3 in number, 58a,54a, and 55a, each one corresponding to and actuated by itscorresponding station-selecting plunger 53 and 54, respectively; butadditional contacts and operating plungers will be provided if desired,one set for each additional station to be pi'e-set. All of these-movablecontacts maybe electrically connected togetherinparallel by wire 52-,and in seri'es through switch 9%, and switch 28 to the ground 22a, andalso through battery or other sourceil and through relay coil ili'to theplate l ia circuit of tube M.

Cathode Me of tube i l ma be connected to extension Bil of the shaft 23of tuning element H, insulated therefrom by suitable insulating coupling8 i, but rotating in syncln'onism with the shaft 28 of condenser H.Cathode E50 may also be connected to fixed contact finger 58c adapted tobe engaged by movable contact 50a. A second fixed contact finger 5%,adapted to be engaged by movable contact 5011, ma be connected to thetop of resistor 5.

Contact Ell?) operates, as will be seen, to remove thesensitivity-reducing bias normally impressed on tube t by the current inresistance 5 and increases the sensitivity of the receiver whensignalseeking plunger 55; is operated, inorder to assure fullsensitivity of the receiver during such operation.

Closure of movable contact 59a against fixed contact finger tile, aswill. be observed, closes the space current path of tube M (from cathode(40' to contact etc, contact 58a, conductor 52, switch Bil, switch 2%,direct-current source'22, relay 15, to anode Ma) so that this tubeca'nbe ionized by incoming signals of predetermined strength-when thecontactsare closedl Otherwise (when the contacts are open), tube i i isdeprived of control since it cannot be ionized with an open spacecurrent circuit.

Plunger 58, when not depressed, is out of'con tact with finger 59a,which is normally biased'to open position in front of fixed contacts 5%and An allowance- Silc (full line position of Fig; 7). for overtravel ismade in'finger 56c so that when plunger 58 is depressed'to the limit ofits movement, finger Etapasses by contacts 5% and 500 to the extremeright hand dott'ed'position in Fig. Land in thispositionfinger 5001'does not make either 5% or 53c.

Plunger 5i: will not remain in'overti'avel position because of thepressure: of the restoring; springsoperatingon theplungeraandwhen theplunger is released, it returns to the latch position determined by cami5 each of the plungers engaged by pivoted latch it actuated by spring.

H. The latch position of plunger 53- isthat in which contact 59a isclosed. against contacts 56b and 500 (middle position of Fig. 7).

The remaining movable contacts 53a, 54a, and 55s,,operated bytheirrespective plungers 53, 5t,

and 55, each of which is allocated to a particular station, aresimilarly provided with latch cam 15" and also are arranged for someovertravel, and spring contacts 53a, 54a, and 55a are preferablynormally slightly inclined forwardly, as shown in Fig. 2 and the dottedposition in Fig. 3. Each of these plungers is provided with an operatingnose which engages the respective finger at an intermediate point andmoves it inwardly when the plunger is latched in.

Shaft extension to carries a number of wiper wings 63 corresponding toeach of the movable contacts, and these may be formed by a metal clipbent at 64 to provide a pair of arcuate shaft-engaging ends 65 and 65with circumferential depressions adapted to engage groove 68 on shaft vextension til, permitting angular displacement of the wings undercertain conditions, but preventing longitudinal shifting.

In the fully out position of any particular station-selecting plunger,the corresponding movable contact is not engaged, and on rotation ofshaft extension 59' each of wings as will pass by its correspondingcontact without making it.

The zones onthe various fingers where contact is made may be slightlydished, as shown (greatly exaggerated for clarity), but this is notnecessary and may be omitted if desired, and the dimensions may be sochosen that each wing makes contact with its corresponding movablecontact through only a small part of its 360 rotation, which willcorrespond to a tuning variation of a few kilocycles, preferably 5 or 6or in any event less than 10.

When any station-selecting plunger is depressed to the latch position,the corresponding finger, such as 53a, is moved inwardly to the fullline position shown in Fig. 3, where contact is just made by wing 53'over a small angular distance as shaft extension 69 rotates.

While any wing engages its corresponding movable contact, the spacecurrent circuit of tube 1 4 is completed from cathode Me to shaftextension 68 to the particular wing and its correspondingmovabl'e'contact, thence through switches and 2B. in series through theB battery 22 and relay iii to anode I la. This contact is so slight thatit does not change the angular position of the wing on the shaftextension.

Each of the plungers except plunger 50 may be provided with a secondoperating nose '59, having two laterally separated portions 29a and 5%.These have no function except in overtravel position, but in suchposition they extend inwardly far enough to engage the outer edges oftheir particular wing 63, as shown in Fig. i, and hold it againstrotation while shaft extension 68 continues to rotate. This, of course,changes the angular position of the wings on the shaft extension.

It will be noted that the wings are made somewhat wider than theircorresponding contacts in order that this operation may occur wheneverany one of the signal-selecting position plungers 54, and 55' is movedto overtravel position. Pushing any station-selecting plunger toovertravel position will open switch so through the action of bail 9!,which en ages movable arm Silo of switch 9i], carrying it out of contactwith stationary arm 9%. This switch and likewise bail 9i are springbiased to the closed position of To switch 90.

' circuit will be completed, and the tuner will scan.

Operation of the receiver may now be understood. Suppose that it is nowturned on, tuned to some particular station and the operator wishes tooperate it as a signal-seeking receiver and is satisfied to receiveanything which the receiver may pick up. He will then depresssignal-seeking plunge 50. The first operation will be to release latchl6, allowing the previously-depressed plunger to return to out position.

This opens space current circuit of tube i4, relay armature 15a moves toback contact position, and the motor begins to turn. It may be notedthat in pushing plunger 50, passing contact will be made by finger Eliaagainst contacts 5% and 530, but this will be only momentary, and bypushing the button to overtravel position the circuits controlled bythese contacts are interrupted.

Thus the motor will continue to operate and the tuner will scan as longas signal-seeking plunger Ell is held in overtravel position, but themotor will be prevented from stopping as long as the button is held inthis position because tube i l cannot be ionized with its space currentcircuit open.

Suppose now the operator removes his finger from plunger 59. It willreturn to the latch position, in which finger 58a makes contact withfingers 50c and 58?), thus closing the space current circuit of tube Hi,preparing the tube to fire on an incoming signal, and removing the biason tube 4, restoring full sensitivity of the receiver.

The receiver will continue to scan until it tunes an incoming signal ofpredetermined strength,

at which time tube l i will fire, armature 15a will move to frontcontact position, opening the motor circuit and declutching the motorand the tuner, and applyin the brake to the tuner and connecting incompensating circuit iii-41.

Also, ground will be applied through front contact i5f2 to the top ofresistor 5. In this particular instance this last action is of nosignificance because this point is already at ground ptential throughclosure of finger 58a against contact th, but it will he of significancein connection with the operation of the apparatus by any other plunger.If the operator is not satisfied with the station thus tuned in, it isonly necessary to push plunger 56 momentarily again, and the receiverwill tune to the next station in the spectrum in the manner justdescribed.

Suppose, however, that the operator now depresses plunger 53,corresponding to a particular local station for which the apparatus hasalready been pre-set or calibrated. The first operation of plunger 53will be to release latch 16, thus restoring any other depressed plungerto out position, and opening the plate circuit of tube it, which startsthe tuner scanning.

The operator may now remove his finger from plunger 53, which is held inlatched-in position, holding finger 53a in depressed position where itwill be engaged by the corresponding wing 63 at some point during itsrevolution. It will be noted that the space current circuit of tube I4is now open through all of the wings, none of which are in contact withtheir respective fingers, and it is also open at contact 5B0, which isno longer engaged by finger 50a.

Consequently, tube I 4 will be deionized, relay armature l5a will be inback contact position, and the motor circuit will be established at b.'The tuner will scan, and nothing further will occur until it comes towithin a few kilocycles of the particular frequency channel on which thedesired local station is operating.

At this time it should be noted that the shortcircuit around resistor 5has been opened at 15;2, and the sensitivity of the receiver is reducedso that only strong signals are being brought in. This eliminates thepossibility of the receiver tuning being terminated by a distant stationin the neighborhood of the frequency of the desired local station.

As soon as wing 63 engages its finger 53a, the space current circuit oftube M is completed and this tube can now be ionized. Since the nextstation which will be received on further operation of the tuner is thedesired station, scannin will continue until the desired signal is tunedin, in response to which tube i l will ionize and close relay l5 onfront contact, stopping the motor, applying the circuit compensation,and restoring full sensitvity to the receiver by short-circuitingresistor 5 through contact [5 2, permitting the receiver to operate atfull sensitivity under the control of any well-known A. V. C. circuit(not shown).

If the operator now wishes to change to another local station, he may,for instance, operate plunger 5 This will, as before, release any otherplungers, open the space current circuit of tube l4, start the tuner inoperation, and also reduces the sensitivity of the receiver. The tunerwill continue to operate until the next wing 63 engages itscorresponding finger 54a, at which time the same kind of operationoccurs and the receiver tuning will be terminated at the newly selectedstation.

It may be noted that failure of the receiver to tune to the desiredstation frequency indicates that the selected station is not operating,and this affords a ready means of determining whether the desiredstation is on the air, as, for example, late at night.

It now remains only to describe how the receiver is preset or calibratedfor particular local stations. In order to do this, the operator mustknow the frequency on which the desired station operates, which he willdetermine from any log book or from the daily newspaper programs.

Having decide, for example, that plunger 53 is to be allocated tostation A, he then pushes plunger 53 into the overtravel position shownin Fig. 4 and holds it there. This releases all other plungers, opensthe plate circuit of tube I 4 at switch 93, reduces the sensitivity ofthe receiver, and starts the tuner. He will continue to hold the plungerin the overtravel position until the dial shows him that he is within afew kilocycles of this station, at which time wing 63, corresponding tofinger 53a, has been engaged by nose 18a and 79b of the plunger and ithas been shifted angularly on the extension of shaft of tuner I I.

He will then release plunger 53, which moves out from overtravelposition to latch position, permitting wing 63 to rotate with shaftextension 60, but before this wing breaks contact with finger 53a, thedesired station will be received, tube M will fire, and the receivertuning will be terminated with the desired station tuned in and withwing 63 in the proper or pre-set angular position for future tuning ofthe same station by the same plunger. The other plungers may be set in asimilar manner and the receiver is then calibrated or preset for theparticular local stations desired.

It is clear that this presetting or calibration operation can best beperformed in the manner 11 described when the particular desiredstations are on the air, as otherwise the tuner will simply continue toscan. However, in this connection it may be pointed out that, althoughthe receiver tuning will not be terminated because the desired stationis not on the air, if the operation has been carried out correctly andthe plunger re leased when the receiver is not more than kc. away fromthe desired station and the tuning is approaching it, the apparatus iscorrectly calibrated, and when next this particular plunger is operatedand the station is on the air, the receiver will accurately tune to it.

If at any time it is desired to reset for difierent stations, this isdone just as already described; and if thermal drift should cause theset to go out of tune slightly after being in operation a while, it isonly necessary to press another button momentarily to start thescanning, then press the desired station button again. The receivertuning will then go through the tuning cycle and stop on the stationdesired, at the correct tuning position, since it is reception of thesignal which determines the stopping position.

While I have shown and described certain preferred embodiments of myinvention, it will be understood that modifications and changes may bemade Without departing from the spirit and scope thereof, as will beclear to those skilled in the art.

In the specification I have explained the principles of my invention andthe best mode in which I have contemplated applying those principles, soas to distinguish my invention from other inventions, and I haveparticularly pointed out and distinctly claimed the part, improvement,or combination which I claim as my invention or discovery.

I claim:

1. In a signal-seeking receiver, in combination,

a power-operated tuner for scanning the spectrum oi said receiver, and acontrol circuit, including a thermionic tube for stopping variation ofsaid tuner in response to reception of a signal of predeterminedstrength, said control circuit being normally ole-activated, said tubehaving its circuits so arranged that variation of said tuner isinitiated whenever said control circuit is deactivated, a plurality ofstation-selecting plungers, and a plurality of switch elements eachoperated by one of said station-selecting plungers to effect activationof said control circuit over a predetermined small portion of thescanning spectrum, each switch element including a portion thereofsynchronized with said tuner for de-activating said control circuit andthereafter reestablishing it once in each tuning cycle over saidpredetermined small portion of the frequency spectrum scanned by saidtuner, said last mentioned switch portions comprising spring clipsangularly adjustable on a shaft synchronized with said tuner.

2. The combination claimed in claim 1, in which said plungers aremovable into the path of said spring clips to adjust them .angularly onsaid shaft.

3. The combination claimed in claim 1, in which said plungers have aswitch-closing position and an overdrive position, in the latter ofwhich they project into the path of said spring clips to cause angularadjustment thereof.

4. The combination claimed in claim 1, in which said plungers have asignal-selecting position and an overdrive position,and which includes aswitch in the space current circuit of said tube,

and means operated by any of said plungers in overdrive position foropening said switch.

5. A signal-seeking receiver comprising: yariable means for tuning saidreceiver to any ireuency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a Wave signal translated by said receiver for deenergizing saidpoweroperated means to terminate variation thereby of said tuning means;and a plurality of station selectors included in said energizing circuitand each comprising switch elements selectably actuated, in synchronizedrelation with the movement of said tuning means, to circuit-openingposition at which said control system is deenergized over the majorportion of said tuning range and to circuit-closing position at whichsaid control system is energized over a preselected small portion ofsaid tuning range to permit said control system over said small portionof said tuning range to effect said deenergization of said poweroperatedmeans.

6. A signal-seeking receiver comprising: variable means for tuning saidreceiver to any frequency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a wave signal translated by said receiver ior-deenergizing saidpoweroperated means to terminate variation thereby of said tuning means;a plurality of station selectors included in said energizing circuit andindividually movable from an inoperative to an operative position; eachof said selectors comprising switch elements selectively actuated, insynchronized relation with the movement of said tuning means, tocircuit-opening position at which said control system is deenergizedover the major portion of said tuning range and to circuitclosingposition at which said control system is energized over a preselectedsmall portion of said tuning range to permit said control system oversaid small portion of said tuning range to efiect said deenergization ofsaid power-operated means; and a plurality of actuators for selectivelymoving said selectors to said operative position thereof to select anindividual small portion of said tuning range within which to permitsaid deenergization of said power-operated means.

7. A signal-seeking receiver comprising: variable means for tuning saidreceiver to any frequency within a predetermined operating frequencrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a wave signal translated by said receiver for deenergizing saidpoweroperated means to terminate variation thereby of said tuning means;a plurality-of station selectors included in said energizing circuit andeach comprising switch elements selectably actuated, in synchronizedrelation with the movement of said tuning means, to circuit-openingposition at which said control system is deenergized over the majorportion of said tuning range and to circuit-closing position at whichsaid control system is energized over a preselected small portion ofsaid tuning range to permit said control system over said small portionof said tuning range to effect and means for adjustably presetting saidsyn- .chronized relation of said each switch elements operated means toterminate variation thereby of said tuning means; a plurality of stationselectors included in said energizing circuit andvindividually movablefrom an inoperative to an operative position; each of said selectorscomprising switch elements selectably actuated, in synchronized relationwith the movement of said tuning means, to circuit-opening position atwhich said control system is deenergized over the major portion of saidtuning range and to circuit-closing position at which said controlsystem is energized over a preselected small portion of said tuningrange to permit said control system over said small portion of saidtuning range to efiect said deenergization of said power-operated means;and a plurality of actuators for selectively moving said selectors tosaid operative position thereof to select an individual small portion ofsaid tuning range within which to permit said deenergization of saidpower-operated means; each of said actuators being movable to anoverdrive position and including means efiective in said overdriveposition for adjustably presetting said synchronized relation of saideach switch elements and said tuning means to adjust the positions ofsaid small portions within said tuning range.

9. A signal-seeking receiver comprising: variable means for tuning saidreceiver to any frequency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a wave signal translated by said receiver for deenergizing saidpoweroperated means to terminate variation thereby of said tuning means;a plurality of pairs of switch elements actuated in synchronizedrelation with said tuning means to a circuit-opening position at whichsaid control system is deenergized over the major portion of said tuningran e and to a circuit closing position at which said control system isenergized over a preselected small portion of said tuning range; and aplurality of station selectors for selectively including individualpairs of said switch elements in said energizing circuit of said controlsystem to permit said control system over said small tuning rangeportion of a selected pair of switch elements to effect saiddeenergization of said power-operated means.

10. A signal-seeking receiver comprising, variable means for tuning saidreceiver to any frequency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a wave signal translated by said receiver for deenergizing saidpoweroperated means to terminate variation thereby of said tuning means;a plurality of switches each including a first relatively fixed switchelement and a second switch element movable in synchronized relationwith said tuning means to provide a circuit-opening position of saideach switch over the major portion of said tuning range and acircuit-closing position thereof over a preselected small portion ofsaid tuning range; and a plurality of station selectors for selectivelyincluding individual ones of said switches in said energizing circuit ofsaid control system to permit said control system over said small tuningrange portion of a selected switch to effect said deenergization of saidpower-operated means.

11. A signal-seeking receiver comprising, variable means for tunin saidreceiver to any frequency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a wave signal translated by said receiver for dcenergizing saidpower-operated means to terminate variation thereby of said tuningmeans; a plurality of switches each including a first relatively fixedswitch element and a second switch element movable in synchronizedrelation with said tuning means to provide a circuit-opening position ofsaid each switch over the major portion of said tuning range and acircuit-closing position thereof over a preselected small portion ofsaid tuning range; and a plurality of station selectors for selectivelyincluding individual ones of said switches in said energizing circuit ofsaid control system to permit said control system over said small tuningrange portion of a selected switch to effect said deenergization of saidpoweroperated means; each of said station selectors including meansoperated thereby for adjustably presetting the synchronized relation ofan individual one of said second switch elements and said tuning meansto adjust the positions of said small portions within said tuning range.

12. A signal-seeking receiver comprising: variable means for tuning saidreceiver to any frequency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and repeatedly over said tuning range; a control systemhaving an energizing circuit and responsive to a predetermined amplitudeof a wave signal translated by said receiver for deenergizing saidpower-operated means to terminate variation thereby of said tuningmeans; a plurality of switches included in said energizing circuit toenergize said control system upon closure of each switch, each of saidswitches having a first switch element rotatable with said tuning meansand a second switch element normally positioned out of engagement withsaid first switch element but movable into the path of travel thereof tomake contact therewith only over a preselected small portion of saidtuning range; and a plurality of station selectors for selectivelymoving individual ones of said second switch elements into the path oftravel of an associated first switch element to permit said controlsystem over said small portions of said tuning range to effect saiddeenergization of said power-operated means.

13. A signal-seeking receiver comprising: variable means for tuning saidreceiver to any frequency within a predetermined operating frequencyrange; power-operated means energizable to vary said tuning meanscontinuously and re- 2,501 ,eoos

peate'dly over said tuning range; :aacontrol system having an energizingcircuit :and responsive vto a predetermined amplitude of .a wave signaltranslated by said a'eceiver for 'deenergizing said power-operated meansto terminate variation thereby of said tuning means; a plurality ofnormally open switches included in said energizing circuit to energizesaid control system upon closure of any one of said switches and therebypermit said control system to effect deenergization of saidpower-operated means; each of said switches having a vfirst switchelement moving, in synchronized relation with the movement of saidtuning means, out of engagement with a second switch element over themajor portion of said tuning range but movable into engagement with saidsecond switch element over a preselected small portion of said tuningrange; said second switch element of each switch being selectivelymovable from a first position at which said :each switch is open for all'positions of said first switch element to a second position at whichsaid each switch is closed over said preselectable small portion oi said"tuning range; and a plu- 16 rality of station selectors for selectivelymoving individual ones of said second switch elements to said secondposition thereof to effect tunin of said receiver to preselectedreceived wave signals within said range.

MARION J. PIFER.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

